Lithologic Reservoirs

Chang 9 oil reservoir set is one of the potential hydrocarbon exploration targets in Longdong area, Ordos Basin, while its reservoir features are not clear and became a constraint on the efficient exploration and development of Chang 9 oil reservoir set. Based on the data of thin section, SEM, vitrinite reflectance and physical properties, this paper studied the reservoir features of Chang 9 oil reservoir set. The results show that the favorable rock types comprise medium to fine-grained lithic arkoses and feldspathic sandstones of underwater distributary channel microfacies, and they are the foundation for the reservoir development. Mechanical compaction and cementation of calcites, quartz, illite/smectite, illite, kaolinite and laumontite occluded the pores in different degrees, and they are the main causes for the reduced porosity and permeability. Early authigenic chlorite rim and illite/smectite rim cements enhanced the capacity of compaction resistance, inhibited quartz cementation, and saved large numbers of primary intergranular pores. Hydrothermal dissolution by deep organic acid has greatest contributions to improve the porosity and permeability of the reservoirs by producing secondary pores, and it is crucial for the development of the high quality reservoirs.

Basic content and future development of seismic reservoirology

WEI Pingsheng， YONG Xueshan， PAN Jianguo， GAO Jianhu， QU Yongqiang， GUI Jinyong

2014, Vol.26(1): 10–17 Abstract ( 479 ) PDF (814 KB) ( 523 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.002

This paper summarized the basic features of the reservoir study in different stages, and revealed that the reservoir study has stepped into the combination stage of the seismology and geology, according to which the seismic reservoirology is proposed. Through deeply analysis of the goal, theory, base, experiment, technique and method of the seismic reservoirology, we believed that the diphase medium theory is the basic theory of the seismic reservoirology, the building of the quantitative relationship between the reservoir and seismic parameters is the core, and the breakthrough of the reservoir seismic experiment is the key to fulfill the task. The future development of the seismic reservoirology is to improve and innovate the diphase medium theory, to build the quantitative relationship between the reservoir and seismic parameters from the aspects of emission and reception of the seismic wave, the wave and ray theory of the seismic propagation, and the combination of forward modeling and inversion, and to realize the final goal of reservoir characterization based on reservoir geology using key techniques.

Characteristics of gravity flow and controlling factors of Chang 6 oil reservoir set in Huachi area, Ordos Basin

LI Fengjie， YANG Chengjin， DAI Tingyong， LI Junwu， YANG Yuchuan

2014, Vol.26(1): 18–24 Abstract ( 549 ) PDF (1008 KB) ( 475 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.003

Based on core observation, this paper analyzed the petrology characteristics and primary sedimentary structure and other sedimentary facies symbols, and concluded that the gravity current sedimentation of Chang 6 oil reservoir set in Huachi area is mainly consist of sandy debris flow and turbidity current sedimentation. These two kinds of gravity current sedimentation stay quite different in their growing location. Sandy debris flow locates in upstream, while turbidity current sedimentation stays in downstairs. This difference leads to the zonation in reservoir characteristics between south and north. Sandy debris flow has lower compositional maturity and interstitial fillings but better reservoir physical properties and oiliness, while turbidity current sandstone reservoir performs by contraries. The types of interstitial fillings of reservoir sand body of Chang 6 oil reservoir set in Huachi area are mostly illite, calcareous cementitious and chlorite film. Sandy debris flow has higher contents of illite and calcareous cementitious, but turbidity sand body possesses higher contents of chlorite film. The main reservoir space of Chang 6 oil reservoir set in Huachi area is primary intergranular pores and intragranular dissolved pores. The surface porosity of sandy debris flood is apparently higher than that of turbidity sand body. The feldspar which consists more sandy debris flood provides more physical foundation of dissolution, thus the content of intragranular dissolved pores in sandy debris flow sand body is larger than that of turbidity sand body.

Study on the regional accumulation differences of Chang 9 oil reservoir set in Jiyuan Oilfield

SHI Jiannan， TANG Guolong， WU Jing， PU Yuhao， LIU Jiang， NIU Xiaobing

2014, Vol.26(1): 25–28 Abstract ( 549 ) PDF (359 KB) ( 552 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.004

The Chang 9 oil reservoir set in Jiyuan Oilfield is a favorable layer to replace for rolling exploration, and there are obvious differences on oil reservoir conditions and enrichment degree in different areas. Based on core observation, logging interpretation, sample testing and related simulation experiments, from hydrocarbon kitchen, the channel between the reservoir and the distance, dynamic, this paper compared and analyzed the hydrocarbon accumulation differences of Chang 9 oil reservoir set in Hongjingzi, Hujianshan and Luopangyuan areas. The results show that Hongjingzi area is near the hydrocarbon source rocks, reservoir properties are also good, source reservoir pressure is strong, so this area is favorable for hydrocarbon enrichment; Hujianshan area has good reservoir properties, but it is relatively distant from the hydrocarbon kitchen, and the source reservoir pressure is small, so hydrocarbon enrichment degree is general; in Luopangyuan area, source reservoir pressure is small, fracture was not developd, and reservoir properties are poor, so hydrocarbon enrichment degree is poor.

Low permeability reservoir characteristics of Chang 8 oil reservoir set in Zhenyuan area, Ordos Basin

TIAN Tian， WANG Haihong， ZHENG Rongcai， HOU Changbing， WANG Changyong

2014, Vol.26(1): 29–35 Abstract ( 589 ) PDF (816 KB) ( 363 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.005

Based on core observation, cast thin sections, scanning electron microscopy and physical properties, combined with well logging interpretation, this paper studied the reservoir characteristics of Chang 8 oil reservoir set in Zhenyuan area, Ordos Basin. The result shows that the reservoir suffered acidic alteration with secondary pores developed. The reservoir space is dominated by remaining primary intergranular pores, intergranular dissolved pores and microcracks. Intercrystalline pores between clay minerals have also a little contribution. The reservoirs are controlled by sedimentary facies, detrital composition, diagenesis and tectonism. The favorable microfacies controlled the spatial distribution of the reservoirs. The clastic composition and grain size are directly related to physical properties. The diagenesis has both good and bad effects. The compaction and cementation made the majority of primary pores lost. The dissolution formed secondary pores which greatly improved the porosity and permeability, and they are crucial to the high-quality reservoirs.

Sequence-based lithofacies paleogeography and sand body distribution of Chang 8 oil reservoir set in Zhenyuan area, Ordos Basin

DUAN Yue， HOU Changbing， ZHENG Rongcai， WANG Haihong， WANG Changyong

2014, Vol.26(1): 36–44 Abstract ( 573 ) PDF (1280 KB) ( 328 )

The Chang 8 oil reservoir set is one of the important reservoirs in Zhenyuan area, Ordos Basin. Based on core observation, well logging and analytical data and previous research results, this paper studied the sedimentary facies of Chang 8 oil reservoir set. The Chang 8 oil reservoir set was deposited by shallow-water braided river delta. Microfacies such as main channels, distributary channel, crevasse splay, underwater distributary channel, interdistributary estuary, depression, mouth bar and distal bar were identified. According to the fine high resolution sequence and stratigraphic framework, we compiled the sequence-based lithofacies palaeogeography maps on the basis of the short-term base cyclic units which were equal to a sublayer sand body, and analyzed the causes, assemblage, distribution and evolution of various types of sand bodies. The results can provide fine depositional and sequence data for the reservoir prediction and efficient exploration and development of the lithologic reservoirs of Chang 8 oilreservoir set in the study area.

Seismic sequence and provenance analysis of the Upper Triassic Xujiahe Formation in AY area, Central Sichuan Basin

CHEN Xiaoer， FAN Kun， XIONG Yan， WANG Xiaolan， WANG Dan， CHEN Dan

2014, Vol.26(1): 45–51 Abstract ( 476 ) PDF (607 KB) ( 344 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.007

AY area which shows a monoclinal structure in the direction of northwest is located in the central part of gentle structure zone, Central Sichuan Basin, Southwest China. This paper carried out seismic sequence research of the Upper Triassic Xujiahe Formation with comprehensive analysis of geological, seismic and well logging data. The result shows that the source of the Xujiahe Formation may be located in the south or southeast of the AY area by means of analyzing onlap direction of seismic event, TWT thickness contour map of seismic sequences and incised valley trend. Sandstone composition data excluded the possibility that Luzhou paleo-uplift become the provenance. We supposed that “Qianzhong ancient land” and “Jiangnan ancient land” may be the source of the Xujiahe Formation in Central Sichuan Basin. This viewpoint gives some hints to the further exploration and prospect of the Xujiahe Formation in Sichuan Basin.

Reservoir sensitivity of Middle Jurassic Toutunhe Formation in Fudong slope, Junggar Basin

LI Yun，QI Liqi，HU Zuowei，WEN Huaguo

2014, Vol.26(1): 52–57 Abstract ( 471 ) PDF (888 KB) ( 510 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.008

Middle Jurassic Toutunhe Formation in Fudong slope is one of the important hydrocarbon objective layers in eastern Junggar Basin. The complex reservoir sensitivity restricted the development of oil and gas. Clay minerals are low in Toutunhe Formation, but the mineral types are rich, and various types of clay minerals are developed. The mixed-layer smectite and illite are most abundant. Through the liquidity experiments, the reservoir has the strongest water sensitivity, followed by salinity sensitivity and acidic sensitivity, which are the main reasons for the reservoir damage. The damage degree of the sensitivities is associated with the types of clay minerals, pore throat and clastic composition. The sensitivity analysis shows the importance of the process of reservoir protection in drilling and testing to reduce formation damage.

Reservoir diagenesis and porosity evolution of the second member of Xujiahe Formation in Suining-Pengxi area

TAO Yanzhong， JIANG Yuqiang， WANG Meng， ZHANG Chun， LI Zhengyong， LIU Shu

2014, Vol.26(1): 58–66 Abstract ( 545 ) PDF (1221 KB) ( 530 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.009

Sandstone of the second member of Xujiahe Formation is an important natural gas reservoir with good exploration prospect in Suining-Pengxi area. The low porosity, low permeability and strong heterogeneity of the sandstone reservoir directly affected the oil and gas exploration and development in this area. Based on slice observation, SEM, inclusion thermometry, vitrinite reflectance and thermal degradeation, this paper systematically studied the types and intensity of diagenesis and porosity evolution of the second member of Xujiahe Fomation. The results show that the sandstone has undergone medium-strong compaction, strong cementation, weak metasomatism and strong corrosion. The reservoir is currently in the middle diagenetic A-B stage and the reservoir was almost completely compacted at middle diagenetic A stage. The pore type is mainly secondary pore. This paper provided geological evidence for favorable reservoir developing area via clear illustration of the process of sandstone reservoir compaction.

Sequence-based lithofacies and palaeogeographic characteristics of Chang 9 oil reservoir set in Longdong area, Ordos Basin

WANG Xinxin， WANG Haihong， ZHENG Rongcai， HOU Changbing， WANG Changyong

2014, Vol.26(1): 67–74 Abstract ( 574 ) PDF (920 KB) ( 393 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.011

Based on comprehensive analyses of core description, thin section observation, paleontology, source area and well logs, this paper studied the characteristics of sedimentary facies and sequence stratigraphy of Chang 9 oil reservoir set in Longdong area, Ordos Basin. It is determined that Chang 9 oil reservoir set belongs to shallow-water fluvial dominated delta system and it can be divided into one long-term, two middle-term and four short-term sequences. On the basis of the quantitative calculation of paleosalinity and its subarea, the position of palaeo-lakeshore during Chang 9 depositional stage was determined. According to the source area, sedimentary facies and sequence, the rising and falling base level phases of middle-term sequence cycles were selected as the isochronic stratigraphic unit to draw up the sequence-based lithofacies and paleogeography map of Chang 9 oil reservoir set in Longdong area. It is concluded that paleogeography features and sand body distribution are controlled by lake level fluctuation and source direction. Distributary channels and underwater distributary channels during the transgressive phases are favorable for reservoir development, and the sand body direction is parallel to the major source direction. The results can guide the following exploration for the Chang 9 reservoirs in Longdong area.

Sedimentary facies of Shaximiao Formation in Hexingchang-Fenggu area at the middle part of western Sichuan Depression

FU Ju， WU Ling， LI Gang， YANG Yingtao， LIU Liping

2014, Vol.26(1): 75–79 Abstract ( 441 ) PDF (554 KB) ( 452 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.011

The Shaximiao Formation in Hexingchang-Fenggu area at the middle part of western Sichuan Depression attained a high degree of attention because of its large scale delta deposition and large exploration potential, but the sediment source and facies is unclear. The rock types and structural features, heavy mineral assemblage, well logging and seismic facies of Shaximiao Formation were analyzed. The result shows that the sedimentary source of Shaximiao Formation is located at the northeast of the study area. Subaqueous distributary channel and interdistributary bay are the dominant sedimentary microfacies, and subaqueous distributary channel is the favorable sedimentary facies. The research results provide basic geologic data for the oil and gas exploration in this area.

Characteristics of low permeability reservoir of Chang 2 reservoir in Xirengou area, Ordos Basin

GAO Chao， SUN Binghua， SUN Jianbo， CAO Cheng， WANG Yongfei，YAN Xiong

2014, Vol.26(1): 80–85 Abstract ( 562 ) PDF (586 KB) ( 342 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.012

Chang 2 reservoir in Xirengou area is typical low permeability reservoir. The sedimentary characteristics, lithology characteristics, reservoir properties, diagenesis types, pore texture and pore types of Chang 2 reservoir in Xirengou area were studied through analyzing the core, thin sections, scanning electronic microscope and physical properties. The result shows that Chang 2 reservoir developed in distributary channel has the characteristics of ultra-fined grain size of the deposits and low maturity, the pore types are mainly primary intergranular pores and secondary d issolved pores, and structural-lithologic trap is the main type of traps. A large number of arenopelitic and calcarenaceous interlayer that developed in the reservoir led to poor vertical differentiation of oil and water, and further separated reservoir, which makes the in-layer heterogeneity become stronger in single oil reservoir. The macro distribution of Chang 2 reservoir is controlled by local structure, reservoir lithology and physical properties.

Reservoir pore types and controlling factors of the fourth member of Quantou Formation in GD area, southern Songliao Basin

DENG Yonghui， CHEN Kaiyuan， LIN Yibing， CHANG Chunying， HUANG Xin， XIAO Peng

2014, Vol.26(1): 86–91 Abstract ( 555 ) PDF (779 KB) ( 383 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.013

In the view of problems that reservoir petrologic characteristics, microscopic pore genetic types and their controlling factors have not been researched clearly in the fourth member of Lower Cretaceous Quantou Formation in GD area, southern Songliao Basin, by comprehensive application of the data of thin section, scanning electron microscope and clay mineral, this paper studied the reservoir pore types and controlling factors. The pores of Quan 4 member in GD area are mainly post compaction residual pores, post cementation residual pores, dissolved intergranular pores and dissolved intragranular pores. The dissolved intergranular pores are formed by the dissolution of intergranular matrix, cements, feldspar and debris, and the dissolved intragranular pores are formed by internal corrosion of feldspar and eutectic part in debris. Tectonic fractures developed locally are quite important to reservoir physical properties. The present pores genetic types are closely correlative with the depositional environment and diagenesis. The sedimentary conditions determine its petrologic feature of fine-grained and mud-rich, and further control the reservoir features of pore primary pores in this area. Compaction is decisive for the remaining primary pores size and volume, cementation is the main factors for destroying the primary pores, and carbonate cementation provides material base for later dissolution. Dissolved pores formed by dissolution are of very important contribution in enhancing the porosity. Based on the analysis of rock thin section and scanning electron microscope, it is considered that the Quan 4 member belongs to reservoir with mixed pores, remaining primary intergranular pores are the dominated reservoir space, later dissolved pores have a crucial role in improving the reservoir properties, and micropores in matrix are of little importance for reservoir properties.

Three-dimensional numerical simulation of electrical imaging logging response in fractured reservoir

CAO Yu，ZHANG Chaomo， ZHANG Zhansong， ZHANG Chong， XIONG Lei

2014, Vol.26(1): 92–95 Abstract ( 546 ) PDF (409 KB) ( 482 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.014

According to the design principle, structure and logging mode of micro-resistivity image logging instrument, this paper studied the electrical image logging response characteristics to fractured reservoir by three-dimensional finite element method, simulated the logging response changes with the fracture width, fracture extension depth, resistivity contrast and fracture dip, and researched the resolution of the instrument to the two horizontal fractures. The results show that the changes of fracture width and resistivity contrast have obvious influence on the logging response. The logging response to high angle fracture appears obvious asymmetry. If the double horizontal fracture spacing is less than five millimeter, they can not be distinguished. This research result is helpful for using electrical image logging to identify and quantitatively evaluate fracture.

Approximate formula of reflection coefficient for small-scale body

LI Shengjun， GAO Jianhu， YONG Xueshan， WANG Yao， WEI Xinjian

2014, Vol.26(1): 96–99 Abstract ( 448 ) PDF (341 KB) ( 518 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.015

AVO technology has become an important means for petroleum exploration after decades of development. In the aspect of finding heterogeneous reservoir, AVO technique plays an irreplaceable role compared with other methods. This paper analyzed the AVO characteristics of the lateral variable small-scale body through wave equation finite difference numerical solution method, and discussed the influences of size variation and speed change of lateral smallscale body on the reflection coefficients. The least square method was used to fit the relations of the reflection coefficient difference with scale body width and scale velocity. The result of error analysis combined with test data shows that the error between fitted formula and the experiment data is less than 0.5%, which indicates the influence of small-scale body width and elastic parameters on the reflection coefficient. The formula can be used to predict the size of small-scale body and rock elastic parameters through AVO abnormalities, and provide protection for the validation of the exact expression of reflection coefficient with velocity change of transverse small-scale body.

Key technologies of seismic imaging and reservoir description for offshore complex fault block: A case study from Wei 12-1 Oilfield in Beibu Gulf Basin

LIU Aiqun， HAO Jianwei， CHEN Dianyuan， WANG Lijun， LU Tongxiang

2014, Vol.26(1): 100–104 Abstract ( 452 ) PDF (475 KB) ( 618 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.016

Wei 12-1 Oilfield is a complex fault block oil field offshore western South China Sea, and it is characterized by complex objective interval fault, complicated reservoir distribution, complicated connectivity and strong heterogeneity. The seismic imaging is unclear, which brings great difficulties to the previous exploration and later reservoir development. This paper carried out studies from the aspects of seismic data imaging processing techniques, interpretative imaging technology and geological modeling, proposed ideas of pre-stack imaging and target imaging processing, and obtained good imaging results by using techniques and methods, such as pre-stack anisotropy depth migration, advantage trace stacking and post-stack frequency imaging and diffusion filtering, and formed a series of key techniques of seismic imaging for complex fault block oil and Gas field. These research results not only have a guiding significance to the further development, deployment and adjustment in Wei 12-1 Oilfield, but also have certain popularization value for the exploration and development in other complex fault block oil and gas field.

Application of Monte-Carlo method to OOIP estimation of an offshore oilfield

LUO Wensheng， SUN Lichun， ZHENG Hongyin， JIANG Baizhao， WU Jing

2014, Vol.26(1): 105–109 Abstract ( 588 ) PDF (525 KB) ( 758 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.017

It is difficult to ascertain every parameter of the OOIP calculation by determination method especially in the initial oilfield development stage because of the limitation of geological data. This paper presented the principle, workflow, and research method of Monte-Carlo method, and analyzed the key points. Taking an offshore oilfield as an example, this paper optimized the best probability distribution model of OOIP calculation parameters through Chisquare test function, determined the high, middle and low values of OOIP parameters by random simulation, and estimated the sensitivity. The applicability of the Monte-Carlo method was discussed finally. The study results show that the Monte-Carlo method is a very effective method to estimate the uncertainty of OOIP based on geological analysis and abundant data sample number, and the method is helpful for estimation of similar oil and gas field in the initial development stage.

Comparative study of high frequency acoustic wave test and dispersion extrapolation of gypsum mudstone in simulated formation

LI Shuanggui， ZHANG Jun， YI Hao， ZHOU Wen， SHAN Yuming， YIN Shuai

2014, Vol.26(1): 110–115 Abstract ( 492 ) PDF (617 KB) ( 418 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.018

In order to obtain the transformational relations between shear wave slowness time and compressional wave slowness time and other statics parameters of the gypsum mudstone of Paleogene in An area of Tarim Basin at 20 kHz, we conducted indoor 1 000 kHz high frequency acoustic wave test, and extrapolate the acoustic wave velocity at 20 kHz based on the tested acoustic wave velocity, quality factor and dispersion equation. The comparative analysis of the acoustic wave or acoustic wave slowness time at these two kinds of frequencies shows that the compressional wave slowness time is closer to logging compressional wave slowness time value under simulated formation condition; the wave velocity and quality factor change slightly within 85 ℃, the changes of wave velocity can be ignored, and the quality factor ranges from 5% to 7%; both the wave velocity and quality factor increase with the increasing of net confining pressure; comparing with compressional under simulated formation conditions and atmospheric pressure, the compressional wave velocity increment is 2.7% to 8.4%, and the compressional wave quality factor increment is 27% to 58%, gypsum mudstone dispersion degree is 7.4% to 24.4% （average 15.12%）, with relatively large dispersion degree. By using the deformation of dispersion equation, we proposed an intuitive expression between quality factor and wave velocity decline of gypsum mudstone under simulated formation condition. According to the influencing factors of gypsum mudstone quality factor, the compressional wave of gypsum mudstone was divided intoⅠ, Ⅱ, Ⅲ three levels of dispersion from high to low, at last dispersion effect was discussed in the application of shear wave slowness time prediction. The results show that under the conditions of 1 000 kHz and 20 kHz frequency, the average relative error of shear wave slowness time predicted by compressional wave slowness time is only 2% within the variation range of gypsum mudstone acoustic time, and the error has the trend of increase with the increasing of gypsum content. The fitting formula of compressional wave slowness to shear wave slowness can be applied to the prediction of shear wave slowness under the two kinds of frequencies. Because the dispersion degree of gypsum mudstone is larger, and the acoustic slowness varies greatly under the two kinds of frequencies, so dispersion calibration should be applied in the actual application.

Application of diffusion filtering method to the seismic data processing

CHEN Keyang， WU Peixi， YANG Wei

2014, Vol.26(1): 117–122 Abstract ( 479 ) PDF (561 KB) ( 524 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.019

Based on anisotropic diffusion filtering equation, this paper presented the corresponding numerical equation, together with its simplest anisotropic diffusion filtering numerical equation. Then, we applied diffusion filtering method to four aspects of application, such as multi-scale low-frequency reverse-time migration noise suppression, seismic reflection wave and scattered wave relatively separating processing, holding fault boundary random noise suppression and pre-stack and post-stack seismic data interpolation processing, and also presented each assumed condition of the applications. The computation results show that the diffusion filtering method can be used to obtain good processing results under different assumed conditions and instruct the practical seismic data digital processing.

Correction of SAGD productivity formula in anisotropic heavy oil reservoir

WANG Dawei， LIU Xiaohong， ZHANG Fengyi， XU Wankun， WU Chunxin

2014, Vol.26(1): 123–126 Abstract ( 558 ) PDF (293 KB) ( 379 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.020

Butler productivity formula for steam assisted gravity drainage （SAGD） assumes that the reservoir is homogeneous and isotropic, without considering the impact of the vertical permeability, which causes that the SAGD production capacity result is higher than the actual value. This paper compared the correction methods of productivity formula for conventional horizontal well in anisotropy reservoir, and carried out the average permeability correction of SAGD productivity formula by using nonlinear regression fitting. The SAGD numerical simulation result was applied to push back the value of the average permeability in the analytical formula, in order to establish the corresponding relations among the average permeability, horizontal permeability and vertical permeability, and finally obtain the expression of permeability in anisotropy reservoir through the regression. The application result shows that the calculation result of the corrected SAGD productivity formula is closer to the true value.

Deduction and application of productivity formula of horizontal wells after acidizing

YUAN Lin， LI Xiaoping

2014, Vol.26(1): 127–130 Abstract ( 655 ) PDF (269 KB) ( 651 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.01.021

During the developing of oil and gas field with horizontal wells, there always exists a damage zone with low or ultra-low permeability near the wellbore. Through acidizing, the permeability near the wellbore will become higher than ever before, eventually the well can get high productivity, so it is of great importance to accurately predict the productivity of horizontal wells after acidizing. Based on the seepage principle, this paper simplified the three dimensional seepage mode of horizontal wells into two two-dimensional seepage, and applied the area equivalence principle, conformal mapping method, complex potential theory and the law of equivalence percolation resistance to deduct a new productivity formula of horizontal wells after acidizing. Through case study and correlation, the results calculated by the new formula and classic productivity formula of horizontal wells are smaller than practical output, but the relative error from the results calculated by new formula is the smallest. So, the new formula is more practical for predicting the productivity of horizontal wells after acidizing. The study can provide new research method for the productivity prediction and dynamic analysis of horizontal wells after acidizing.